Chimneys

ABSTRACT

A chimney comprising a corrugated outer shell, an inner shell incorporating a section having corrugations at desired spacings so as to compensate for any unequal expansion between the outer shell and the inner shell, and fiber-glass or other suitable heat insulation medium packed into the space between such shells, of which the following is a specification.

G Miiitefil tiates Patent 1 i 1 Potter May 3, i973 1 CHIMNEYS 2,526,09710/1950 Sveinson ..98/46 n l,6l5,9()9 2/1927 Nance ..l26/307 InventPaar'ck 25 ommwmd 2.102.727 12/1937 Maher .237/55 Avenue, Hamilton, NewZealand [22] Filed: Aug. 4, 197i Primary Examiner-William F. ODeaAssistant Examiner-Peter D. Ferguson [211 App! 168385 Almrney lrvinThompson and Robert Patch [52] US. CL. .98/60, 110/184, LIX/I49 [57]ABSTRACT [51] lnt.Cl. ..E04h 112/28 A Chimney Comprising a CorrugatedOuter Sm" an {58] Field of Search ..98/586(),45,46; 126/307; I 1

l w 49 inner shell incorporating a section having corrugations 237/55110/ l at desired spacings so as to compensate for any unequal expansionbetween the outer shell and the Referenms Cited inner shell, andfiber-glass or other suitable heat insu- UNTED STATES PATENTS lutionmedium packed into the space between such shells, of which the followingis a specification. 36%](19 8/[887 Dewey 126/307 R UX 11 Claims, 4Drawing Figures Patented May 1, 1973 3,730,073

3 Sheets-Sheet l FIGJ.

Patonted May 1, 1973 s sheets-sheet 2 FIG.2.

Patented May '1, 1973 3 Sheets-Sheet 5 FIG 3 cniMNEYs This inventionrelates to improvements in chimneys.

A problem especially associated with chimneys of plants burning highsulphur-content fuels is that of corrosion and smut emission. When thefuel is burnt, the sulphur content forms oxides which will condense attemperatures normally ranging from 240-280F. to form sulphuric acid onthe cooler surfaces of chimneys passing exhaust gas to atmosphere. Acidcondensate deposited in this manner is the cause of the extensivecorrosion found in the higher sections of steel chimneys. In addition,smuts will be formed by a build-up of minute particles of carbon on thislayer of sulphuric acid and will lift off to enter the gas stream todischarge to atmosphere. Such smuts will create a nuisance to thelocality by settling on the surfaces of buildings, paintwork, motorcars,etc., where they will cause staining and acid attack.

To prevent corrosion and to obviate the formation of acid smuts, it isnecessary to maintain the inner surface of the chimney at temperaturesabove the acid dewpoint of the exhaust gases and to discharge the gasesto atmosphere at the highest possible efflux velocity in order to obtaingood conditions for dispersal With the advent of the high efficiencyboiler discharging exhaust gases at temperatures as low as lF. above thesteam temperature, the problems of corrosion and smutting have becomemore difficult to control. Moreover, as the head on a boiler is reducedbelow its designed maximum, then the exhaust gas temperatures arecorrespondingly lowered and the problems of corrosion and smutting willbecome more acute. By cladding the exterior of the chimney with analuminum liner to form an insulating air gap of some inch wide, controlof corrosion and smutting has been possible for modern boilers withloads of 75 percent of the related maximum output. At boiler loads below75 percent of the rated maximum output, a modern high efficiency boilerwill produce acid condensation in an aluminum-clad stack with theresulting detrimental effects of corrosion and smutting. It has,therefore, become increasingly obvious that a more efficient form ofinsulated chimney must be provided if a better control of exhaust gastemperatures is to be achieved. In this respect, observations ofchimneys insulated with a layer of rockwool up to 2 inches thick hasshown that positive control of corrosion and smut emission can beachieved with boiler loads below 50 percent of the rated maximum output,and that an insulated chimney is far superior to a chimney clad inaluminum with an air gap only.

The object of the present invention is to provide a chimney having sucha construction and or arrangement of its parts that in use it willpractically overcome the adverse conditions created by low temperatureacid condensation in a high efficiency boiler.

Generally the invention consists of a chimney comprising a corrugatedouter shell, an inner shell incorporating a corrugated sectionat'desired spacings so as to compensate for any unequal expansionbetween the outer shell and the inner shell, and fiber-glass or othersuitable heat insulation medium packed into the space between suchshells.

In further describing the invention, reference will be made hereinafterto the accompanying diagrammatic drawings, in which:

FIG. 1 is a longitudinal sectional view of the chimney shown broken inits height.

FIG. 2 is a cross-section of part of the chimney showing a typical jointbetween sections of the chimney length,

FIG. 3 is a similar view to FIG. 2 but showing a modified sectiondesigned as a free-standing chimney, and

FIG. 4 is a cross-section taken on the line 4-4 of- FIG. 3 on a reducedscale.

In giving effect to a preferred embodiment of the invention, the outershell 10 of the chimney is corrugated by horizontal rolls 11 and formedout of sheet stainless steel, such as 166 type 304. Dependent upon thesize of the chimney, the outer shell 10 can be built up by 4 footstandard lengths fully welded at length joints.

The inner shell 12 of the chimney consists of sections 13 constructed inmolybdenum austenitic sheet stainless steel, such as 20G. Type 316. Thisinner shell is fabricated to form a one-piece gas-proof structureincorporating peripheral swages 20 at desired intervals, such as every 2ft, to compensate for the unequal expansion between the outer shell 10and the inner shell. The inner shell 12 is affixed to the corrugatedouter shell 10 by a lower outwardly-flanged end 15 being tack-welded tobrackets on the inner face of the outer shell, whilst the upper end ofeach section 13 is located inside the lower end of an upper inner shellsection and fully-welded.

AS already mentioned the space between the outer shell 10 and the innershell 12 is packed with fiberglass 16.

The chimney further includes a vortex or venturi top unit 17 alsoembodying partially corrugated outer and inner shells 18 and 19 formedof the same steels as earlier described. The inner shell 19 of this topis formed with one or more peripheral swages 20 for strength. The lowerend of the shells 18 and 19 of the top 17 are arranged to co-incide withthe top end of the constituted chimney stack of the outer and innershells 10 and 12, and secured thereto through an angle 21 welded to theouter surface of the inner shell 12 and jointing the outer shell 10 andtop outer shell 18. Angles 22 also rigidly connect the upper end of theshells 18 and 19 of the top unit 17, and which angles 22 have bracketswith holes 23 for affixing a cord spark arrestor or other conventionalunit (not shown). The space between the shells l8 and 19 of the top unit17 is also packed with fiberglass 14.

In a modification, as shown in FIGS. 3 and 4, vertical stiffeners 25 areincorporated in the space between outer and inner shells 10 and 12 ofthe chimney stack. The number and size of the stiffeners 25 aredependent upon the height and siting of the chimney. Each stiffenerconsists of a suitable length of channel section steel positioned withone of its webs welded to the outer shell 10 and its lower end welded toa bottom plate 26 and outer angle 27 or angles welded to such plate andsuch shell. This angle 27 has holes drilled for securing by bolts 28 toa similar upper end of an upper section of the stack and through anasbestos ring 24.

With this chimney in operational use it will overcome the adverseconditions created by low temperature acid condensation in a modern highefficiency boiler. It has many advantages over a conventional chimney.Not only does this improved chimney incorporate the principle ofinsulation, but it also employs its own particular form of constructionin materials more resistant to acid attack. The structural strength ofthe chimney is economically obtained by corrugating the outer shell instainless steel to produce a strong light-weight section,self-supporting to the extended heights recommended by the Clean Air Actand impervious to atmospheric attack. The inner shell 12 is made up ofstainless steel sections 13 with a very high elevated creep strength ofany standard stainless steel available and has an improved corrosionresistance to acid attack.

The fiberglass packing l4 and 16 between the respective shells providesoverall thermal conductivity approximately to 0.17 B.T.U.s. per sq. ft.per hour per F. Comparative thermal efficiencies for a bare metalchimney and for an aluminum clad chimney would be about 1.08 and 0.66.The special venturi or vortex top 17 of the chimney obtains the highvelocities for efflux for good dispersal.

in comparison with the convention chimney, this improved chimney willcontrol corrosion and smut emission as well as increase effluxvelocities. The insulating properties will be about 6.5 times greaterthan a bare chimney and about 4 times greater than an aluminumcladchimney. it is maintenance free, both inside and outside. The chimneyslightweight form of construction allows it to be easily handled. Withits structural strength being on the exterior of the chimney, it is lessliable to damage during erection and service and will retain constantlyits appearance. For the same height, its initial cost will be doublethat of a conventional chimney but its maintenance free life will beextended to the life of the plant it services.

What is claimed is:

1. An insulated chimney comprising a thin outer shell, said thin outershell having corrugations therein to increase the structural modulus ofsection of a thin shell by maintaining the section round in the plane ofbending, a thin gauge inner liner formed with corrugations atpredetermined spacings sufficient to compensate for the differentialexpansion between the cool structural outer shell and the hot innerliner, and insulating material disposed between said outer shell andsaid inner liner.

2. A chimney as claimed in claim 1 wherein the outer shell is corrugatedby horizontal rolls.

3. A chimney as claimed in claim 1 and wherein the inner shell consistsof at least one section fabricated to form a one-piece gas-proof shellincorporating peripherally extending swages at desired intervals.

4. A chimney as claimed in claim 3 and wherein the inner shell isaffixed to the corrugated outer shell by a lower outwardly flanged endwelded to brackets on the inner face of the outer shell whilst the upperend of each inner section is located inside the lower end of an upperinner shell section and welded thereto.

5. A chimney as claimed in claim 1 and further including a vortex orventuri top unit also embodying outer and inner shells, and fiberglassor other suitable insulation medium packed mto the spaces between suchshells.

6. A chimney as claimed in claim 5 and wherein the inner shell of thetop unit is formed with one or more peripherally extending swages.

7. A chimney as claimed in claim 5 and wherein the lower end of theshells of the top unit are arranged to co-incide with the top end of theconstituted chimney stack and secured thereto by angles welded to theouter surface of the inner shell and jointing the said outer shell andthe top outer shell.

8. A chimney as claimed in claim 7 and wherein angles alsorigidlyconnect the upper end of the shells of the top unit and have bracketswith holes for affixing a cord spark arrester.

9. A chimney as claimed in claim 1 and wherein vertical stiffeners arepositioned in the space between outer and inner shells of the chimneystack.

10. A chimney as claimed in claim 9 wherein the stiffeners are welded tothe outer shell and to steel rings, at the end of each liner section,the rings being welded to both rings and to an external angle or angles.

11. An insulated upright elongated chimney, comprising a thin metalouter shell, said outer shell having horizontal corrugations thereinthat are rounded in the plane of bending, a thin gauge metal inner linerdisposed within said outer shell, said liner having horizontalcorrugations therein spaced apart by portions of the liner that arestraight in an upright direction, and insulating material packed betweensaid outer shell and said inner liner.

1. An insulated chimney comprising a thin outer shell, said thin outershell having corrugations therein to increase the structural modulus ofsection of a thin shell by maintaining the section round in the plane ofbending, a thin gauge inner liner formed with corrugations atpredetermined spacings sufficient to compensate for the differentialexpansion between the cool structural outer shell and the hot innerliner, and insulating material disposed between said outer shell andsaid inner liner.
 2. A chimney as claimed in claim 1 wherein the outershell is corrugated by horizontal rolls.
 3. A chimney as claimed inclaim 1 and wherein the inner shell consists of at least one sectionfabricated to form a one-piece gas-proof shell incorporatingperipherally extending swages at desired intervals.
 4. A chimney asclaimed in claim 3 and wherein the inner shell is affixed to thecorrugated outer shell by a lower outwardly flanged end welded tobrackets on the inner face of the outer shell whilst the upper end ofeach inner section is located inside the lower end of an upper innershell section and welded thereto.
 5. A chimney as claimed in claim 1 andfurther including a vortex or venturi top unit also embodying outer andinner shells, and fiberglass or other suitable insulation medium packedinto the spaces between such shells.
 6. A chimney as claimed in claim 5and wherein the inner shell of the top unit is formed with one or moreperipherally extending swages.
 7. A chimney as claimed in claim 5 andwherein the lower end of the shells of the top unit are arranged toco-incide with the top end of the constituted chimney stack and securedthereto by angles welded to the outer surface of the inner shell andjointing the said outer shell and the top outer shell.
 8. A chimney asclaimed in claim 7 and wherein angles also rigidly connect the upper endof the shells of the top unit and have brackets with holes for affixinga cord spark arrester.
 9. A chimney as claimed in claim 1 and whereinvertical stiffeners are positioned in the space between outer and innershells of the chimney stack.
 10. A chimney as claimed in claim 9 whereinthe stiffeners are welded to the outer shell and to steel rings, at theend of each liner section, the rings being welded to both rings and toan external angle or angles.
 11. An insulated upright elongated chimney,comprising a thin metal outer shell, said outer shell having horizontalcorrugations therein that are rounded in the plane of bending, a thingauge metal inner liner disposed within saiD outer shell, said linerhaving horizontal corrugations therein spaced apart by portions of theliner that are straight in an upright direction, and insulating materialpacked between said outer shell and said inner liner.